[2 Feb 2025]
i originally released? version 1 of the "WA8LMF TNC Test CD" ? in 2006, with with a slight update, version 1.1, in 2009.
This was an image file that created an audio CD.? The disk contains a variety of recordings of packet APRS transmissions to verify/compare the performance of packet TNCs (both hardware and software).? Over the past 16 years it has become sort of a de-facto standard for testing/comparing various packet radio receiving systems.
In 2009, computer CD systems were plagued with cheap unstable software-based audio decoding (the infamous "AC97" codec) that used system interrupts for timing. The audio sample rate would actually vary, depending on CPU loading and the number of tasks currently running on the computer.
On the other hand, AUDIO CD players (even cheap boomboxes and DiscMan portables) used stable crystal-controlled time-bases. In 2009, I chose to produce the disk as an audio CD?? (not a CD-ROM with .WAV files)? to yield more accurate and repeatable tests of TNC performance.
The ver 1.1. CD was produced in the "CD-Extra" format that combines CD audio tracks playable on a music CD player -- with a data CD-ROM area accessible with a computer CD/DVD drive.? (This hybrid format is sometimes used on modern music CDs to include song lyrics, artist bios, etc on the disk along with the music.)
??? Some users have had problems with recording the BIN/CUE format of the TNC Test image file to physical CDs.? (This now-somewhat-obscure disk-image format was required because the more-common .ISO disk image format can't handle the mixed-mode half-music-CD/half-CD-ROM format of the disk.)
Today, the "horsepower" of the average computer has increased orders of magnitude since 2009. More importantly, for the last decade or so, most computers have been equipped with the "RealTek HD" audio chips that use an accurate crystal-controlled time-base. As a result, computer-playback of audio files is now very accurate with stable sample rates.
I have now re-released the Test CD as a standard CD-ROM in the common .ISO image format. This disk contains the identical test audio tracks, but now stored as lossless FLAC files.? The .ISO image file can be used to burn a physical CD.? Or the .ISO file can be used as-is,? "mounted" as a virtual CD-ROM drive using an used drive letter on your system. Or the FLAC-format? audio files could be copied to a flash drive.
I have extensively revised the page on my web site for the Test CD .? It now includes download links for both the original ver 1.1 audio CD image, and the new ver 2.0? .ISO CD-ROM image.
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Stephen H. Smith wa8lmf (at) aol.com
Skype:??????? WA8LMF
EchoLink:? Node #? 14400? [Think bottom of the 2-meter band]
Home Page:
New? 30 Meter?? APRS-over VARA? Frequency
As of 1 Jan 2025.?? Details Here:
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- APRS over VARA? --
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"Studio B" Ham Shack on Wheels
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